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Diffstat (limited to 'virt/kvm/kvm_main.c')
-rw-r--r--virt/kvm/kvm_main.c26
1 files changed, 13 insertions, 13 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index d54f6578a849..0f1f1c7c7a36 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -874,30 +874,30 @@ static struct kvm_memslots *install_new_memslots(struct kvm *kvm,
int as_id, struct kvm_memslots *slots)
{
struct kvm_memslots *old_memslots = __kvm_memslots(kvm, as_id);
- u64 gen;
+ u64 gen = old_memslots->generation;
- /*
- * Set the low bit in the generation, which disables SPTE caching
- * until the end of synchronize_srcu_expedited.
- */
- WARN_ON(old_memslots->generation & 1);
- slots->generation = old_memslots->generation + 1;
+ WARN_ON(gen & KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS);
+ slots->generation = gen | KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS;
rcu_assign_pointer(kvm->memslots[as_id], slots);
synchronize_srcu_expedited(&kvm->srcu);
/*
- * Increment the new memslot generation a second time. This prevents
- * vm exits that race with memslot updates from caching a memslot
- * generation that will (potentially) be valid forever.
- *
+ * Increment the new memslot generation a second time, dropping the
+ * update in-progress flag and incrementing then generation based on
+ * the number of address spaces. This provides a unique and easily
+ * identifiable generation number while the memslots are in flux.
+ */
+ gen = slots->generation & ~KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS;
+
+ /*
* Generations must be unique even across address spaces. We do not need
* a global counter for that, instead the generation space is evenly split
* across address spaces. For example, with two address spaces, address
- * space 0 will use generations 0, 4, 8, ... while * address space 1 will
+ * space 0 will use generations 0, 4, 8, ... while address space 1 will
* use generations 2, 6, 10, 14, ...
*/
- gen = slots->generation + KVM_ADDRESS_SPACE_NUM * 2 - 1;
+ gen += KVM_ADDRESS_SPACE_NUM * 2;
kvm_arch_memslots_updated(kvm, gen);